1. Field of the Invention
The present invention relates to control apparatuses for internal combustion engines mounted on vehicles etc. and in particular, to a control apparatus for a direct injection type internal combustion engine.
2. Background Art
Current vehicles (automobiles) have been required to reduce exhaust gas substances contained in exhaust gas of the automobiles, such as carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx), and to reduce fuel consumption from the viewpoint of environmental protection. A direct injection type engine has being developed for the purpose of reducing the above.
The direct injection type engine reduces exhaust gas substances and fuel consumption, improves engine power, etc. by directly performing fuel injection with a fuel injection valve into a combustion chamber of a cylinder.
However, in the direct injection type engine, fuel spray that moves in the combustion chamber by injection tends to adhere to a crown surface of a piston and a wall surface of a cylinder bore. An adhesion amount of the fuel spray depends on a timing of fuel injection by the fuel injection valve.
If assuming the timing of fuel injection by the fuel injection valve as an intake stroke, when the timing of fuel injection is relatively advanced, while a time period for fuel vaporization between fuel injection and ignition is ensured to be able to improve combustibility, fuel adhesion to the crown surface of the piston increases since the fuel injection is performed at the time of the crown surface of the piston being closer to an injector. Particularly, the fuel having adhered to the crown surface of the piston is gradually atomized at the time of subsequent engine combustion, and then discharged out of the cylinder in a state of incomplete combustion (JP Patent Publication (Kokai) No. 2007-32326 A).
In addition, when much fuel is remained in the combustion chamber in a state of adhering to the crown surface of the piston and the wall surface of the cylinder bore, graphite is generated, and the number of particle matter, so-called Particulate Matter (hereinafter referred to as PM) particles to be discharged tends to increase. Here, Number of particles means the total number of PM particles to be discharged when driving a vehicle with a predetermined driving pattern. Particularly, when much fuel adheres to the crown surface of the piston, Number of particles tends to increase. In recent years, there has been growing need to reduce Number of particles with respect to engines for vehicles and in particular, to direct injection type engines.